I'm not saying that the option to map your above layout should be phased out completely, your layout should be an optional layout also. It's also true that your layout would be practical for some games..to an extent, but imagine using your layout in games such as doom. Using the Q (left-up) etc diagonals would produce unpredictable movement and in fighters for eg, if you want to short jump, a key mapped to right-up would not suffice, you'd have constant long jumping since UP-right etc is automatically processed when the key E is pressed.

To short jump you have to temporarily tap 'right' and then 'up' quickly this can easily be done by my explained layout in the first post of this thread. Also your layout would create stiff movement in 2d scrollers like star soldier and other similar games. Movement would be stiff and or unpredictable in games like doom, tony hawks pro skater etc. My idea layout could be used as a more universal layout where as your explained layout would be practical for selected games.

Q = left-up......, W = up......., E = right-up
A = left ..........., S = ............, D = right
Y = left-down..., X = down..., C = right-down

vs

Q = Left, W = UP, E = RIGHT
A = LEFT, S = DOWN, C = RIGHT

A Universal controller....simple yet effective....
their is also this idea layout I had:

Q = left-up......, W = up.......,. E = right-up
A=LEFT.........., S = DOWN,.. C =RIGHT

But this also may only be practical for selected games...
Then again our two ideas for movement should first be implemented in an actual n900 game of each type (eg scroller, fighter, rpg etc) and tested to see which would be more practical. I did my control tests on computer emulators to see which would be more suitable for thumbs on n900...